A fork lift truck is widely used for carrying or lifting a heavy object or a pallet in a warehouse, factory or office. This fork lift truck has wheels and is self-propelled, and can carry a heavy object without resorting to manpower, i.e. another operator, thereby contributing to ease of loading and unloading. Since this fork lift truck is required to lift the heavy object, it has a mast mechanism or counterweight thereon, which makes it heavy, thereby preventing it from traveling fast on a highway. Accordingly, the fork lift truck travels only within a limited area such as a factory or warehouse. As a result, the traveling speed of the fork lift truck when it carries the heavy object thereon is about 20 to 30 km/h which is relatively slow compared with other vehicles. When it is self-propelled for a long distance, it takes much time. If the loading or unloading operations are performed at other locations, another fork lift truck is required.
If the fork lift truck travels on a public road, it is necessary to obtain permission (such as a vehicle number plate) from a competent authority. However, when the fork lift truck is used only in the factory or warehouse, such permission is not necessary in many cases. Accordingly, when the fork lift truck is moved from one factory or warehouse to another factory or warehouse, it is customary to load the fork lift truck on a bed of a truck which is qualified to travel legally on a highway.
Furthermore, when the fork lift truck is carried to a destination while loaded on the truck, if another fork lift truck is not provided at the destination, the carried fork lift truck must be unloaded from the truck with the help of other operators. However, due to shortage of manpower, the freight or cargo often cannot be unloaded from the truck. In such case, the fork lift truck is located on the truck bed together with other freight and the fork lift truck and other freight are unloaded from the truck bed at the destination, which is effective and reduces the burden imposed on the operator.
As mentioned above, if the fork lift truck can be loaded on the truck bed, it is very convenient since it can be useful for loading or unloading other freight or cargo. However, since the fork lift truck per se is relatively large in bulk and has the counterweight, etc., it is heavy. Accordingly, if the fork lift truck is loaded on the truck bed, it is lifted by a crane or by a long plate bridging between the bed and the ground. Such an operation is troublesome and requires an exclusive device for loading the fork lift on the truck bed, which impedes a quick loading operation.